What is the chance of UDP-alpha-D-glucose and UDP-beta-D-glucose formation in One-Pot in vitro reaction catalyze by series of enzymes from beta-D-glucose as primary precursor.
Is there any chance of changing anomeric forms of glucose (change in beta-D-glucose when alpha-D-glucose was used as precursor sugar and vise versa)?
Is there any effect of acidic or basic solutions over change in anomeric forms of glucose during reaction catalyses?
If I understand your question correctly, are you asking about interconversions between the alpha and beta forms of free glucose in solution? If so, then the answer is definitely Yes, once dissolved in water, either form of glucose will undergo anomerization until the solution reaches an equlibrium mixture of approximately 1/3 alpha-D-glucopyranose and 2/3 beta-D-glucopyranose, with much smaller amounts of alpha and beta D-glucofuranose, as well as tiny amounts of the open-chain aldehyde form. This reaction is accelerated by the presence of acid or base. However, most enzymes that I know of are very specific for one form or the other, so for example, an alpha-D-glucosyltransferase will not catalyze the synthesis or breakdown of the beta-D-glucoside. The presence of trace amounts of other contaminating enzymes, however, may make it appear so.
Thank you very much for your precise answer Greg Cote.
My supposition is If the goal is to synthesize UDP-beta-D-glucose.
As you said there is presence of 2/3 portion of beta-D-glucopyranose which suggests the maximum possibility of formation of UDP-beta-D-glucose than UDP-alpha-D-glucose.
Are you saying that the enzymes (GTs) are specific enough to accept either UDP-alpha-D-glucose or UDP-beta-D-glucose as donor substrate for glycosylation reaction?
I appreciate your answer if available with references.
Thank you Greg Cote for your answer once again. Now I am more curious to know whether it is impossible to make UDP-beta-D-glucose from beta-D-glucose enzymatically? Is there any state or condition to control the self-inter conversions between alhpa- and beta- anomeric forms of free glucose in solution?
An enzyme that starts with a beta anomeric form of a substrate and ends up making a beta-anomeric form is called a retaining-type of enzyme, since the anomeric form of the substrate is retained in the product. If it begins with an alpha-anomeric form of the substrate and ends up making a a beta-anomeric form of the product, it is called an inverting-type of enzyme. Whether an enzyme is retaining or inverting depends on its mechanism, which depends on its sequence and structure. Both types exist in nature, although I'm not sure if that applies to your particular enzyme. To respond to your question about making UDP-beta-D-Glucoside from free beta-D-glucose, you need some energy source to produce the high-energy UDP-Glc bond, regardless of which anomeric form of glucose is present. That typically occurs by coupling of the synthetic reaction to hydrolysis of some other high-energy bond, like a sugar phosphate, etc.
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